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Jan. 24, 1956 R. w. KREBS ETAL CONVERSION OF HYDROCARBON OILS WITH THEUSE OF FLUIDIZED SOLID PARTICLES Filed on. 31, 1950 QEGENE QATOQ,

ExTQAN 5005 I GASES Qobemt (D .Krebs QFICLPLQS L'l. IQLmbev-IindrrCltborneg United StatesPatentO CONVERSION OF HYDROCARBON OILS WITH THEUSE OF FLUIDIZED SOLID PARTICLES Robert W. Krebs and Charles N.Kimberlin, 31"., Baton Rouge, La., assignors to Esso Research andEngineering Company, a corporation of Delaware Application October 31,1950, Serial No. 193,062 6 Claims. (Cl. 196-52) The present inventionrelates to amethod and apparatus for treating hydrocarbon oils. Moreparticularly, the invention pertains to the production of gasoline aswell as higher boiling distillate fractions from heavy hydrocarbon oilsof the type of topped or reduced crude or similar heavy residues. In itsbroadest aspect the invention provides for contacting heavy residues ofthe type mentioned with hot subdivided fluidized solids at temperaturesconducive to the coking and cracking of the residues and producing thevapors and gases required for fluidization by pre-cracking a portion ofthe residue feed. I

In refining crude oil it is standard practice first to subject the crudeto simple distillation or topping to produce various distillatefractions, such as naphtha, heating oil and gas oil cuts boiling up toabout 800950 F. Most of these distillate fractions are normallyconverted into high quality gasoline range motor fuels by suchconventional treatments as thermal and/ or catalytic reforming andcracking, or similar operations.

The residue from the crude distillation may be processed to yieldvaluable high molecular weight materials including lubricating oils,waxes, resins, fuel oils, asphalt, etc. depending on the origin andcharacter of the crude. More recently, however, the demand for motorfuels has increased so greatly that it has become extremely difficult tosatisfy the motor fuel market by merely processing crude distillates inthe manner indicated above. This situation has prompted considerableresearch and development work directed toward an efficient conversion ofcrude residua into additional quantities of motor fuels. The two mostcommon methods used for this purpose in current practice areviscositybreaking and coking of reduced crude.

Viscosity-breaking involves a treatment-of reduced crude or the like atelevated temperatures for ashort period of time adequateforthe'formation of an addi- Broadly, the present invention is concernedwith such improvements.

One of the major difliculties complicating a successful coking operationresults f1 om the heavy deposition of coke in the coking vessels andtransfer lines requiring frequent and time-consuming cleaning periods.This problem has been solved or at least greatly alleviated, prior tothe present invention, by admixing with the residuum to be cokedsubstantial proportions of a subdivided inert adsorbent solid, such aspetroleum or other coke, pumice, kieselguhr, spent clay, sand, or thelike, which serves primarily as a carrier for the coke formed so as toprevent coke deposition on equipment walls and also as a scouring agentremoving coke deposits from the walls. The high surface area provided bythese solids in some cases as, for example, with spent clay, alsoaccelerates'and intensifies the cracking reaction whereby larger yieldsof'gasoline within short holding times may be obtained without anydanger of deactivation of the solids by'carbon deposits or ashconstituents of the feed. The coke deposited on the solids may be burntoff in cyclic or continuous two-vessel operation to gen tional quantityof gas oil .and about 5..15% of gasoline'.

The gas oil forms a suitable feed stock for-thermal. or catalyticcracking and may be converted into gasoline in this manner. However,extensive cracking facilities in addition to the crude still andvis-breaking units are indispensable for the production of satisfactoryquantities of gasoline by vis-breaking of reduc ed crude.

The other method, i. e., coking of reduced cr u de is a much moredrastic heat treatment usually carried out at higher temperatures,ofsay, about 800 1000 F. and for longer times. It results in directproduction of increased proportions of gasolineof, say, about l535% inaddition to gas oil and hydrocarbon gases together with solid coke. Thisprocess lends itself more readily than vis-breaking to the purpose ofproducing-'maximurn' amounts of gasoline from reduced-crude-in' themost' economical manner, particularly in'vie'w' of the fact thatsufficient coke is produced to supply by combustion the heatrequirements of the process. Therefore, the re search eiiorts oftheindustry mostrecently.'have con-l1 erate and supply to the cokingvessel'the heat required for coking.

While fixed bed and suspensoid systems have been suggested for this typeof operation, the so-called fluid solids technique offers greatestadvantages with respect to temperature control, heat economy, ease andcontinuity of operation and equipment dimensions. This technique in itsapplication to the coking of reduced crude involves the injection of thefeed into a relatively dense highly turbulent bed of hot subdividedsolids having a particle size of about 30-400 mesh, fluidized by a gasflowing upwardly through the bed at a linear superficial velocity ofabout 0.23 ft. per second to give the bed the appearance of a boilingliquid separated by a definite interface fro-m an upper dilutesuspension of solids in gases and gasiform products. Volatile cokingproducts are'removed overhead and further treated after the removal ofentrained solids. In some of the adaptations of the process, .cokecarrying solids are continuously passed to a fluid type combustion zonewherein they are fluidized by a combustion-supporting gas and coke isburnt oil to heat the solids to a temperature higher than cokingtemperature. Hot solids are continuously r'ecirculated to the cokingzone in amounts suflicient to supplymost of the heat required therein.

While this procedure affords excellent heat control and utilization aswell as better yields of desirable products as compared to othersystems, certain difliculties arise in connection with the fluidizationof the heat carrying solids. It is necessary to fiuidize these solidsbefore the heavy residue feed is introduced into the reactor. For. thispurpose, steam or inert gas, such as fluegas or recirculated process gashave been proposed in the past. Substantial amounts of these extraneousfluidizing gases are required, particularly when operating at relativelylowtemperatures of, say, less than ll00 P. which have been found'to behighly beneficial for establishing a de-. s'irable product distributionin the eflluent ofthe coking" zone. For'example, expedimental dataindicate that in cracking vacuum residua over inert solids attemperatures below 1000 F., more than 35 wt. per cent of steam based onresidue charged is required to prevent excessive coke deposition andloss of fluidization. Even at temperatures as high as 1'l00 F.'the'minimun'rfluidizing j steam requirement is about-"10 20 wt. percent; The

provision of llu'idizing g ases' 'in these proportions adds considerablyto the costof the cracking process. The present-invention substantallyalleviates thisdifficulty'. It is, therefore, the principal'object ofthe'present' invention to provide an improved fluid-type process andapparatus for coking and cracking crude residua or similar materialswherein the amount of extraneous fluidizing gas required may besubstantially reduced. Other and more specific objects and advantageswill appear from the description below wherein reference will be made tothe accompanying drawing, the single figure of which is asemi-diagrammatic illustration of a system adapted to carry out apreferred embodiment of the invention.

In accordance with the present invention, at least a substantialproportion and preferably at least a major proportion of the fiuidizinggas required for the fluidization of hot solids contacted with the heavyresidue to be coked is produced by gasifying a minor proportion of theresidue feed. For this purpose, a minor proportion of the residue feedis contacted with a narrowly confined, i. e., small diameter, dense,fluidized bed of hot solids at conditions conducive to substantiallycomplete gasification by vaporization and cracking, of all gasifiableconstituents of said minor feed proportion. The vapors and gases soproduced are passed upwardly through an expanded, i. e. large diameter,dense fluidized bed of hot solids superimposed on, and in direct contactwith, said confined bed in such a manner that the gases leaving theconfiincd bed properly fluidize the expanded bed. The remainder of theresidue feed is fed directly to the upper expanded bcd. Properfluidization of the lower confined bed, particularly in its lowerportions may be accomplished by supplying a relatively small amount ofan extraneous fiuidizing gas, such as steam or recycle gas to the bottomportion of the confined bed. Because of the small diameter of thisconfined bed the total amount or extraneous fluidizing gas required forproper fiuidization of this bed is substantially smaller than that whichwould be required to fluidize a solids bed of uniform diameter butsufiicient hold-up to coke and crack the entire teed supplied thereto ina single stream. When operating in this manner, proper fluidization maybe accomplished without the requirement of excessive amounts ofextraneous fiuidizing gas, such as steam, even when operating atrelatively low temperatures of, say, about 850-l050 F. The invention,therefore, has particular utility in connection with this type of lowtemperature operation.

In accordance with the preferred embodiment of the present invention,solids heated in a fluid-type combustion zone to a temperature above thedesired coking and cracking temperature, say to a temperature of about900- 120G F., are first contacted with about 5-30% of the heavy residuefeed stock in a lower constricted portion of a fluidized solids bed soas to accomplish substantially complete gasification and coking of thefeed therein. A small amount of steam or other fluidizing gas may be fedto this portion of the fluid bed to establish a proper fluidizing gasvelocity of about 1-l0 ft. per second. The temperature in theconstricted portion should be relatively high, say about l000l150 F. andthe feed residence time about t to 5 seconds when calculated as a vapor.The upper expanded portion of the fluidized bed may be maintained at thedesired relatively low coking and cracking temperature of about 8501050F., the gaseous efliuent of the lower zone serving to fluidize the upperportion of the bed so that the remainder of the residue feed may besupplied thereto without the danger of fluidization troubles.Substantially larger vapor residence times of, say, about 5-60 secondsare provided in the upper portion of the fluidized bed. The treatingtemperatures mentioned may be readily maintained by continuously passinghighly heated solids from the combustion zone to a lower portion of theconstricted bed and from there into the expanded portion of the bed.However, a substantial, and in many cases even a major portion, of thetotal hot solids required for this purpose may be directly supplied fromthe combustion zone to a lower portion of the upper expanded portion ofthe fluidized bed. The

relative dimensions of the two beds of different diameter should be suchthat the amount of extraneous gas added to the constricted zone plus thegas produced therein by cracking and vaporization are sufficient toestablish a proper fiuidization velocity of about 0.2-3 ft. per secondin the upper expanded bed. The solids used for the purposes of theinvention may be either inert, such as petroleum coke, sand, pumice,etc., or catalytic, such as activated clays, synthetic silica-alumina orsilica magnesia composites. and the like.

The advantage secured by this type of operation is highly significant.For example, a process may normally require 10 wt. percent of steam forproper fluidization in a reaction vessel of uniform diameter. Theaverage molecular weight of the products of complete gasification of thefeed may be of the order of 15 to 45. A typical figure often used incalculations is 28. The total fluidizing gas requirement may, therefore,be supplied by subjecting merely 16% of the residuum feed to completegasification in accordance with the invention. This percentage may becalculated 'by applying the ratio of molecular weights to the percentageof steam which would otherwise be used, e. g.

Having described its objects and general nature, the invention will bebest understood from the more detailed description hereinafter in whichreference will be made to the accompanying drawing.

Referring now to the drawing, the system illustrated therein essentiallycomprises a reactor 5 and a heater 30,

, the functions and coaction of which will be presently described usingthe coking and cracking of a 2.4% South Louisiana residuum as anexample. It should be understood, however, that the system may beemployed to a similar treatment of other feed stocks in a generallyanalogous manner. While heater 30 is of conventional cylindrical designsuitable for fluid-type dense phase drawoif operation, reactor 5consists of a small-diameter lower cylindrical section A and acylindrical large-diameter upper section B. The ratio of the diametersof sections A and B may be about 0.1 to 0.4 and the ratio of the heightsof sections A and B about 0.3 to 1.

In operation, the reduced crude is supplied to the system from line 1essentially in the liquid state at a temperature of about 500-800 F. Thefeed is divided into two portions. A major proportion of, say, about 80to is supplied directly to a lower portion of section B of reactor 5,preferably by means of suitable spraying devices, via manifold lines 7.The remainder of the feed .is supplied via line 9 in a similar manner toa lower portion of section A of reactor .5 at a point above distributingmeans such as perforated plate or grid 11 arranged in the bottom ofsection A. Simultaneously, highly heated solids such as coke, sand or acontact clay, having a fluidizable particle size of about 30400 mesh,suspended in a fluidizing gas such as steam are supplied from line 13through grid 11 at a temperature of about ll00-1500 F., preferably aboutl2001300 F., as will appear more clearly hereinafter. About 0.1 to 0.3parts of steam and about 5 to 20 parts of solids supplied through line13 per part of the total reduced crude feed supplied to section A arenormally adequate for the purposes of the invention.

The hot solids entering section A through grid 11 are first contacted insection A with the minor feed portion supplied through line 9. As aresult of the relatively high temperature of the solids and therelatively high solids: feed ratio in secion A, the liquid feed isimmediately vaporized and extensively cracked in section A so that ahighly turbulent fluidized solids mass MA is formed therein having anapparent density of about 10 to 30 lbs. per cu. ft. and providing for avapor residence time of about 1 to S'seconds. For the typeand particlesize of the solids here involved, the dimension of section A may bechosen to establish linear superficial vapor velocities in mass MA ofabout 1 to 10 ft. per second. Heat is absorbed in section A by thevaporization and cracking reaction with the efiect that the temperatureof mass MA is fairly uniform at about l050-1150 F.

Under the influence of the continuous feed of hot solids to the bottomofsection A, fluidized solids flow upwardly into section B. Immediatelyupon entering section B, substantially at the temperature of mass MA thesolids are contacted with the major portion of the reduced crude feedsupplied through manifold 7. Thereupon vaporization, coking and crackingtakes place. Additional vapors and gases are formed and coke is deposited on the solids. However, inspite of the increased amounts ofgases and vapors present in zone B, their.

linear superficial velocityis maintained within a range of about 0.3 to2ft. per second, suitable for fluidization so that a dense turbulentmass MB having an apparent density of about 20 to 60 lbs. :per cu. ft.and a' definite upper interface L5 is formed within section B above massMA. As a result of the endothermic reactions taking place in massMB, thetemperature of the latter may be readilymaintained at the desirablelower level .of about 850 1000 F. "The hold-up of mass Mn may be such aswill provide for a vapor residence time of about 5 to 60 sec. therein.In this manner, proper fluidization is assured even at the relativelylow temperatures of mass MB while using only about of the amount ofsteam which would be required for'proper fluidization of mass MB in theabsence of the'small diameter lower section A. A'mixture of gasiformreaction products and'steam containing about 0.001 to 0.02 lbs. per cu.ft. of suspended solids fines flows overhead'from interface L5 and maybe subjected to gas-solids separation in any suitable equipment, such asa cyclone separator 15. Separated solids fines may be returned to massMB via dip-pipe 17. Product vapors and gases now substantially free ofentrained solids may be passed via line 19 to conventional productrecovery equipment (not shown).

Fluidized solids carrying coke deposited at a rate of about 5 to 25 lbs.per 100 lbs. of residium fed may be withdrawn from well 21 throughstandpipe 23, stripped and aerated with small amounts of a suitable gas,such as air, flue gas, steam, etc., supplied through taps t in a mannerknown per se. The withdrawn solids may be passed from standpipe 23 intoline 25 at a rate similar to that of the solids supply via line 13. Line25 receives a combustion-supporting gas, such as air and/ or oxygen,from line 27 in amounts adequate to permit the removal of about 0.5 to3.0% of coke from the solids by combustion. About 140 to 200 standardcu. ft. of air per pound of carbon are normally suitable for thispurpose. The relatively dilute suspension of solids-in-air or the likemay be passed from line 25 through a distributing device 29 similar togrid 11 into the lower portion of heater 30 to form therein a densefluidized mass M30 similar in appearance and behavior to mass MB.Combustion of coke taking place in heater 30 is so controlled that thesolids in mass Mac are reheated to a temperature of about 11001500 P.which should be at least 50 F. higher than the temperature of mass MA.Flue gases containing entrained solids fines and flowing overhead fromlevel L30 may be passed through gas-solids separator 32 and thence vialine 34 to any desired purpose. Separated solids may be returned to massM30 via dip-pipe 36 or discarded via line 38. The fluidized solid whichis preferably used in the process is coke. Under the usual conditions,more coke is produced in the reaction vessel than is needed to supplythe heat for the process through combustion in heater 30. The excesscoke is withdrawn through line 38 and may then be used for any desiredpurpose. In the event that an extraneous solid, such as a clay or sand,is used, it is often advantageous "via taps t.

6 to withdraw a stream of that material bearing an appreciable amount ofcarbon so that it may be regenerated or burned .in outside equipmentboth for recovery of the solid and the potential heat in the carbon.Make-up sol.- ids may be added via line 40.

Fluidized solids may be withdrawn from heater 30 at the temperature ofmass Mzothrough well 42 and stand: pipe 44 aerated and/or stripped withsteam or inert gas The reheated solids pass from standpipe 44 into line13 wherein they are picked up by fluidizing gas, particularly steamsupplied through line 46, to be fed to section A of reactor 5 asdescribed above.

When catalysts, such as activated clay or a synthetic silica-alumina,are used in place of, or in addition to, the inert solids'referred toabove, care should betaken to avoid catalyst deactivation by overheatingthe same in the carbon-burning state. This may be accomplished bymaintaining the heater temperature at a level not substantiallyexceeding 1200 F. or at an even lower temperature. The reduction intemperature may be com: pensated for .by increasing the catalystcirculation rate, thus keeping the quantity of heat transferredsubstantially constant. When it is desiredto supply a portion, forexample, say, 50-90% of the solids reheated in heater 30 directly to theupper expanded section B of reactor 5 this may be accomplished by meansof line 50 leading into the bottom of section B. Other modificationswithin the spirit of the invention may appear to those skilled in theart.

- The invention willbe further illustratedby the following specificexample.

Example Section A Section B Pitch Rate, B/D Reactor Vessel Diameter, Ft-4. 5 -15 Bed Height, Ft

Pressure, Lb./Sq. In. Ga-. 30 25 Fluid Bed Density, Lb./Cu 20 50 PitchWeight Space Velocity 3. 6 0. 7 Fluid Coke Feed Rate, LbJMi 2,310 11,550 Avg. Temperature of Coke entering Bed, F 1,150 1, 140 Temperature ofBed, F. 1, l, 040 Coke/Oil Feed Ratio 10 5. 6 Wt. Percent Steam on Feed5 0. 5 Superficial Velocity of total gases at inlet, Ft./Sec. 5. 9 0. 5

At the above conditions good fluidization is obtained in the mainreaction zone B with the use of only 0.5% steam on feed, fiuidizationbeing accomplished mainly by the action of the cracked products from thelower reaction zone A.

The above description and exemplary operations have served to illustratespecific embodiments of the invention but are not intended to belimiting in scope.

What is claimed is:

1. In the process of producing distillate fractions from heavy residualhydrocarbon oils by contacting heavy residual hydrocarbon oil at cokingconditions with a dense turbulent mass of subdivided hot solidsfluidized by an upwardly flowing gasiform medium, the improvement whichcomprises introducing an original gasiform medium, which is only a minorpart of the total fluidizing medium required, into the bottom of thedense turbulent mass, supplementing said medium by producing a majorproportion of said gasiform medium requirements by contacting a minorproportion of liquid heavy residual hydrocarbon oil for a relativelyshort time with a narrowly confined fluidized mass of said hot solidsmaintained at 7 a relatively high coking temperature and fluidized at arelatively high linear gas "velocity, said minor proportion of liquidbeing introduced above the bottom of said mass and separately from theoriginal gasiform medium so as to coke and gasify said minor proportionsubstantially completely within said short time, passing gases soproduced into a laterally expanded second mass of hot solidssuperimposed on and in direct contact with said first named mass, thetwo masses constituting a single uninterrupted fluidized bed, so as tofiuidize said second mass at a relatively low linear gas velocity,supplying a major proportion of the heavy residual hydrocarbon oildirectly to said second mass, contacting said major oil proportion withsaid second mass for a relatively long time sufficient for convertingsaid major oil proportion into distillate oils and coke, recoveringdistillate oils overhead from the fluidized bed, passing coke-carryingsolids from said bed to a combustion zone, burning coke off saidcoke-carrying solids in said combustion zone to reheat said solids to atemperature substantially higher than said relatively high cokingtemperature and returning at least a portion of the solids so reheatedto said first named mass to supply said hot solids thereto.

2. The process of claim 1 in which a portion of 'said reheated solids ispassed directly to said second mass.

3. The process of claim 1 in which the feed ratio of solids to oil insaid first named mass is substantially greater than the feed ratio ofsolids to oil in said second mass.

4. In the process of producing distillate hydrocarbon fractions and cokefrom heavy hydrocarbon oil by contacting said oil at a cokingtemperature range of about 350 to 1050 F, with a mobile mass ofnon-catalytic preheated solids of fluidizable particle sizes, theimprove ment which comprises very substantially reducing inertfluidizing gas requirements by establishing a fluidized bed of saidsolids of narrow cross-section in its lower portion and broadercross-section in its upper portion, introducing at the bottom of saidbed a relatively small stream of extraneous inert gasiform fluidizingmedium which is suflicient to start fiuidizing the bed at its narrowbottom part but inadequate to fluidize it at a broader higher level,introducing in liquid state part of the heavy oil to be coked into thenarrow lower portion above the bottom and separately from the inertgasiform medium, continuously supplying hot solids to the lower portionto vaporize and crack the oil so fed and to provide vapors forsubstantially supplementing the bed-fluidizing action of the inertgasiform medium, and introducing a further part of the heavy oil as aliquid spray directly to the broader upper portion of the bed forconversion to distillate and coke.

5. Process according to claim 4 wherein the solid particles arepredominantly coke particles produced in the process.

6. Process according to claim 4 wherein part of the coke produced iswithdrawn from the system as product and part is reheated and returnedto the fluidized bed for continuing the process.

References Cited in the file of this patent UNITED STATES PATENTS2,360,622 Roetheli Oct. 17, 1944 2,379,711 Hemminger July 3, 19452,382,755 Tyson Aug. 14, 1945 2,402,875 Cornell June 25, 1946 2,436,486Scheineman Feb. 24, 1948 2,446,678 Voorhies Aug. 10, 1948 2,460,404 WardFeb. 1, 1949 2,461,958 Bonnell Feb. 15, 1949 2,707,702 Watson May 3,1955 FOREIGN PATENTS 577,831 Great Britain June 3, 1946

1. IN THE PROCESS OF PRODUCING DISTILLATE FRACTIONS FROM HEAVY RESIDUALHYDROCARBON OILS BY CONTACTING HEAVY RESIDUAL HYDROCARBON OIL AT COKINGCONDITIONS WITH A DENSE TURBULENT MASS OF SUBDIVIDED HOT SOLIDSFLUIDIZED BY AN UPWARDLY FLOWING GASIFORM MEDIUM, THE IMPROVEMENT WHICHCOMPRISES INTRODUCING AN ORIGINAL GASIFORM MEDIUM, WHICH IS ONLY A MINORPART OF THE TOTAL FLUIDIZING MEDIUM REQUIRED, INTO THE BOTTOM OF THEDENSE TURBULENT MASS, SUPPLEMENTING SAID MEDIUM BY PRODUCING A MAJORPROPORTION OF SAID GASIFORM MEDIUM REQUIREMENTS BY CONTACTING A MINORPROPORTION OF LIQUID HEAVY RESIDUAL HYDROCARBON OIL FOR A RELATIVELYSHORT TIME WITH A NARROWLY CONFINED FLUIDIZED MASS OF SAID HOT SOLIDSMAINTAINED AT A RELATIVELY HIGH COKING TEMPERATURE AND FLUIDIZED AT ARELATIVELY HIGH LINEAR GAS VELOCITY, SAID MINOR PROPORTION OF LIQUIDBEING INTRODUCED ABOVE THE BOTTOM OF SAID MASS AND SEPARATELY FROM THEORIGINAL GASIFORM MEDIUM SO AS TO COKE AND GASIFY SAID MINOR PROPORTIONSUBSTANTIALLY COMPLETELY WITHIN SAID SHORT TIME, PASSING GASES SOPRODUCED INTO A LATERALLY EXPANDED SECOND MASS OF HOT SOLIDSSUPERIMPOSED ON AND IN DIRECT CONTACT WITH SAID FIRST NAMED MASS, THETWO MASSES CONSTITUTING A SINGLE UNINTERRUPTED FLUIDIZED BED, SO AS TOFLUIDIZE SAID SECOND MASS AT A RELATIVELY LOW LINEAR GAS VELOCITY,SUPPLYING A MAJOR PROPORTION OF THE HEAVY RESIDUAL HYDROCARBON OIL